Magnetic resonance imaging apparatus

Abstract

In specific magnetic resonance imaging, magnetization spins are repeatedly excited by excitation pulses, and echoes are repeatedly generated after each of the excitation pulses. The echoes so generated are acquired as echo signals. Based on these echo signals, image data is reconstructed. According to the present invention, the number of times the magnetization spins are excited by the excitation pulses is input by an operator and, based on this input number, the number of echoes generated by one excitation is determined. Image-pickup time can easily be computed on the basis of the number of times of excitation and the time required for repeating fixed excitation pulses. The operator is able to easily control the image-pickup time by controlling the input number of times of excitation.

What is claimed is: 
     
       1. A magnetic resonance imaging apparatus comprising: means for repeatedly exciting magnetization spins by excitation pulses;   means for repeatedly generating echoes after each of the excitation pulses;   means for acquiring the echoes generated by said generating means, as echo signals;   means for reconstructing image data based on the echo signals acquired by said acquiring means;   input means for receiving the number of times of excitation the magnetization spins are excited by the excitation pulses; and   means for determining the number of echoes generated by one excitation based on the number of times of excitation received by said inputting means.   
     
     
       2. The apparatus according to claim 1, wherein said determining means determines the number of echoes based on both the number of times of excitation input by said inputting means, and the number of times of phase encoding necessary for reconstructing the image data. 
     
     
       3. The apparatus according to claim 2, wherein said determining means determines the number of echoes based on a result obtained by dividing the number of times of phase encoding by the number of times of excitation. 
     
     
       4. The apparatus according to claim 2, wherein said determining means determines the number of echoes in accordance with a formula:   {(Nencode+Ncontrast)/2}/Nexcite     where Nexcitation is the number of times of excitation, Nencode is the number of times of phase encoding, and Ncontrast is the number of times of phase encoding close to zero encode which is dominant over image contrast.   
     
     
       5. The apparatus according to claim 2, wherein the number of times of phase encoding is input by said inputting means. 
     
     
       6. The apparatus according to claim 1, wherein said determining means determines the number of echoes based on the number of times of excitation and a matrix size.